Design And Synthesis Of Functionalized Covalent Organic Framework Materials And Application In Catalysis

The design and synthesis of well-defined porous structures with orderly arrangement has been a hot topic in the field of materials chemistry in recent years.An outstanding representative of porous materials,covalent organic frameworks provide a molecular platform for the integration of organic structural units into an ordered arrangement of skeletons to create periodic skeletons and unique pores.Thanks to the unique structure of COFs,they have excellent characteristics such as large specific surface area,permanent pores,excellent thermal and chemical stability and high crystallinity.In addition,the backbone and pores of COFs are pre-designed by topography to synthesize predictable structures and achieve unique properties and functions.More importantly,the COFs were functionalised by both post-modification and bottom-up modification strategies to obtain covalent organic frameworks with a homogeneous distribution of active sites and specific functions.Therefore,covalent organic frame materials are widely used in various fields.In the catalytic reaction,the permanent pore of COFs not only provides a channel for the reaction and accelerates the transport of reactants and products,but also provides a reaction site for the contact between the reactants and the active site,enlarges the reaction area,and thus accelerates the catalytic reaction.In our research programme,we designed and synthesised COF-based catalysts by both post-modification and bottom-up approaches,and investigated their catalytic performance.1.In response to the increasing demand for energy and environmental pollution,there is an urgent need to find a clean,renewable energy source.In recent years,solar energy has shown great potential as a clean energy source involved in photocatalytic reactions.However,most conventional photocatalysts require the assistance of precious metals to be photocatalytically active,and the reactions are mostly homogeneous and poorly reusable,which is a limitation.Therefore,the development of a multiphase photocatalyst without metal involvement is of great importance.In the second chapter of our work,we synthesised a D-A type covalent organic framework(BTT-BTDDACOF)consisting of an electron donor unit and an electron acceptor from the bottom up via the Schiff base reaction.It has been shown that the introduction of D-A structure in COFs can lead to significant delocalization of charge within the conjugated skeleton molecules,and the resulting polymers exhibit a narrower band gap and significantly enhanced light absorption in the near infrared region.In addition,BTT-BTDDA-COF has good photocatalytic activity and is effective in converting phenylboronic acid to phenol under visible light irradiation.2.COF-based catalysts with excellent catalytic activity are constructed by precisely introducing active sites into the COFs material backbone through a postmodification strategy.In the third chapter of our work,we synthesised an extended twodimensional COF polymer with side chain functional groups and acceptable orderliness.The introduction of adjacent hydroxyl groups and the unique imine bonding of 2D COF materials allows 2D polymers to have spatially ordered potential chelating centres that are attractive in catalytic applications when complexed with transition metals.3.The design and synthesis of metal-free covalent organic framework materials and their application to the photocatalytic synthesis of organic small molecules is of great importance.In the fourth chapter of our work,we synthesized BTT-DATP-COF.The successful synthesis of the porous material was subsequently demonstrated by characterization tests.The successful synthesis of photocatalytic benzimidazole small molecules demonstrates the photocatalytic activity of COF materials.Important implications for the preparation of metal-free photocatalysts.